quiry, the real caufe of them has not been difcovered.

About twenty years ago, feveral. fires broke out, within a fhort fpace of time, in a rope-walk, and in fome wooden houfes, at St. Petersburgh; and, in all thefe inftances, not the fighteft trace of wilful firing could be found but there was lying in the rope-walk, where the cables for the navy are made, a great heap of hemp, among which a confiderable quantity of oil had been careleffly fpilt, and it was therefore declared fpoilt; for which reafon it had been bought at a low price, and put up together, and was held to be the caufe of the fire. The inferior inhabitants of that part of the town had likewife bought of this fpoilt hemp, at a cheaper rate than ufual, for cloting the chinks, and caulking the windows of their houfes, which are conftructed of balks laid one upon the other. At this rope-walk, coils of cable have been found hot, and the people have been obliged to feparate them, to prevent farther danger.

It was in the fpring of the year 1780, that a fire was difcovered on board a frigate lying in the road off Cronstadt; which, if it had not been timely extinguifhed, would. have endangered the whole fleet. After the fevereft fcrutiny, no caufe of the fire was to be found; and the matter was forced to remain without explanation, but with strong furmifes of fome wicked incendiary being at the bottom of it. In the month of Auguft, in the fame year, a fire broke out at the hemp-magazine at St. Petersburgh, by which feveral hundred thoufand poods of hemp and flax were confumed.

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The walls of the magazine are of brick, the floors of ftone, and the rafters and covering of iron; it ftands alone on an island in the Neva, on which, as well as on board the hips lying in the Neva, no fire is permitted. In St. Peterfburgh, in the fame year, a fire was difcovered in the vaulted fhop of a furrier. In thefe fhops, which are all vaults, neither fire nor candle is allowed, and the doors of them are all of iron. At length the probable caufe was found to be, that the furrier, the evening before the fire, had got a roll of new cere-cloth, (much in ufe here for covering tables, counters, &c. being easily wiped and kept clean,) and had left it in his vault, where it was found almoft confumed.

In the night, between the 20th and 21st of April, 1781, a fire was feen on board the frigate Maria, which lay at anchor, with feveral other fhips, in the road off the island of Cronftadt; the fire was however foon extinguithed; and, by the feverest examination, little or nothing could be extorted concerning the manner in which it had arifen. The garrilon was threatened with a fcrutiny that fhould coft them dear; and, while they were in this cruel fufpenfe, the wildom of the fovereign gave a turn to the affair, which quieted the minds of all, by pointing out the proper method to be purfued by the commiffioners of inquiry, in the following order to Count Chernichef.

"When we perceived, by the report you have delivered in of the examination into the accident that happened on board the frighte Maria, that, in the cabin where the

fire broke out, there was found parcels of matting, tied together with packthread, in which the foot of burnt fir-wood had been mixed with oil, for the purpose of painting the fhip's bottom, it came into our mind, that, at the fire which happened last year at the hemp-warehoufes, the following caufe, among others, was affigned, that the fire might have proceeded from the hemp being bound up in greafy inats, or even from fuch mats having lain near the hemp: therefore, neglect not to guide your farther inquiries by this remark.”

As, upon juridical examination, as well as private inquiry, it was found that, in the fhip's cabin, where the smoke appeared, there lay a bundle of matting, containing Ruffian lamp-black, prepared from fir-foot, moistened with hemp-oil varnish, which was perceived to Have fparks of fire in it at the time of the extinction, the Ruffian admiralty gave orders to make various experiments, in order to fee whether a mixture of hemp-oil varnish and the forementioned Ruffian black, folded up in a mat and bound together, would kindle of itself.

They thook forty pounds of firwood foot into a tub, and poured about thirty-five pounds of hempoil varnifi upon it; this they let ftand for an hour, after which they poured off the oil. The remaining mixture they now wrapped up in a mat, and the bundle was laid clofe to the cabin, where the midhipmen had their birth. To avoid all fufpicion of treachery, two officers fealed both the that and the door with their own feals, and ftationed a watch, of four fea-officers, to take notice of all that pafled the whole night through; and, as foon as any

fmoke fhould appear, immediately to give information to the com mandant of the pört.

The experiment was made the 26th of April, about eleven o'clock A. M. in prefence of all the officers named in the commiffion. Early on the following day, about fix o'clock A. M. a fmoke appeared, of which the chief commandant was immediately informed by an officer; he came with all poffible fpeed, and, through a fmall hole in the door, faw the mat fmoking. Without opening the door, he difpatched a mellenger to the members of the commiffion; but, as the fmoke became ftronger, and fire began to ap pear, the chief commandant found it neceffary, without waiting for the members of the commiffion, to break the feals and open the door. No fooner was the air thus admitted, than the mat began to burn with greater force, and prefently it burst into a flame.

The Ruffian Admiralty, being now fully convinced of the felf-enkindling property of this compofition, tranfmitted their experiment to the Imperial Academy of Scien ces; who appointed my friend Mr. Georgi, a very learned and able adjunct of the Academy, to make farther experiments on the fubject, and to him I am chiefly indebted for this account; though, being my felf at the time upon a vifit to fome of my old parishioners at Cronftadt, I made myself acquainted with many of the circumstances on the fpot.

The experiments of this ingenious chymift are of great importance, as they form a valuable addition to out knowledge on the fubject; and are very remarkable from the occa• fion that led to thefe difcoveries.

Previous to the relation of the experiments, it is neceffary to obferve, that the Ruffian fir-black is three or four times more heavy, thick, and unctuous, than that kind of painter's black which the Germans call kien-rahm. The former is gathered at Ochta, near St. Peterburgh, at Mofco, at Archangel, and other places, in little wooden huts, from refinous fir-wood, and the unctuous bark of birch, by means of an apparatus uncommonly fimple, confifting of pots without bottoms fet one upon the other; and is fold very cheap. The famous fine German kien-rahm is called in Ruffia Holland's black. In what follows, when I fpeak of raw oil, it is to be understood of linfeedoil or hemp-oil; but moft commonly the latter. The varnish is made of five pounds of hemp-oil boiled with two ounces and a half of minium. For wrapping up the compofition, Mr. Georgi made ufe of coarfe hemp-linen, and always fingle, never double. The impregnations and commixtures were made in a large wooden bowl, in which they flood open till they were wrapt up

in linen.

That I may not be too prolix, I will felect and communicate only fuch of the experiments as were moft remarkable, and fucceeded beft.

Three pounds of Ruffian fir-black were flowly impregnated with five pounds of hemp-oil-varnish; and, when the mixture had flood open five hours, it was bound up in linen. By this procefs it became clotted; but fome of the black remained dry. When the bundle had lain fixteen hours in a cheft, it was obferved to emit a very naufeous, and rather putrid fmell, not quite unlike that

VOL. XXXVII.

of boiling oil. Some parts of it became warm, and fteamed much; this fteam was watery, and by no means inflammable. Eighteen hours after the mixture was wrapt up, one place became brown, emitted fmoke, and directly afterwards glowing fire appeared. The fame thing happened in a fecond and a third place; though other places were fcarcely warm. The fire crept flowly around, and gave thick, grey, ftinking fmoke. Mr. Georgi took the bundle out of the cheft, and laid it on a ftone pavement; when, on being expofed to the free air, there arofe a flow burning flame, a fpan bigh; with a strong body of fmoke. Not long afterwards there appeared, here and there, feveral chaps, or clefts, as from a little volcano, the vapour fluing from which burft into fiame. On his breaking the lump, it burst into a very violent flame, full three feet high, which foon grew lefs, and then went out. The fmoking glowing fire lafted for the space of fix hours; and afterwards the remainder continued to glow without fmoke for two hours longer. The grey earthy afhes, when cold, weighed five ounces and a half.

In another experiment, perfectly fimilar to the foregoing, as far as relates to the compofition and quantities, the enkindling did not enfue till forty-one hours after the impregnation: the heat kept increasing for three hours, and then the accenfion followed.

It is worthy of remark, that these experiments fucceeded better on bright days than on fuch as were rainy: and the accenfion came on more rapidly.

In another experiment, three pounds of Ruffian fir-black were [*F]

flowly

flowly impregnated with three pounds of raw hemp-oil; and the accenfion enfued after pine hours.

Three quarters of a pound of German rahm were flowly impregnated with a pound and a half of hemp-oil varnish. The, mixture re mained feventy hours before. it be came hot and reeking. It, then gradually became hotter, and emitted a strong exhalation; the effluvia were moift, and not inflammable. The re-action lafted thirty-fix hours, during which the heat was one while ftronger, and then weaker, and at length quite ceased..

Stove or chimney foot, moftly formed from birch-wood smoke, was mingled with the above-mentioned fubftances and tied up; the compound remained cold and quiet.

Ruffian fir-black, mixed with equal parts of oil of turpentine, and bound up, exhibited not the leaft reaction or warmth.

Birch-oil, mixed with equal parts of Ruffian fir-black, and bound up, began to emit a volatile fmell; but the warmth foon went off again.

From the experiments of the Admiralty, and of Mr. Georgi, we learn, not only the decifive certainty of the felf-accenfion of foot and oil, when the two fubftances are mixed under certain circumflances, but allo the following particulars.

Of the various kinds of foot, or lamp-black, the experiments facceeded more frequently and furely with the coarfer, more unctuons, and heavier, like Ruffian painter's black, than with fine light German rahm, or with coarfe chimney-foot. In regard to oils, only thofe experiments fucceeded which were made with drying oils, either raw or boiled. The proportions of the foots to the oils were, in the fuc

cefsful experiments, very various; the mixture kindled with a tenth, a fifth, a third, with an equal, and likewife with a double proportion of oil. In general, however, much more depends on the mode of mixture, and the manipulation; and, as Mr. Georgi often obferved, on the weather: for, in moit weather, the bundles, after becoming warm, would frequently grow cold again.

It is in all refpects remarkable, that it fhould never till now have been obferved, that a mixture which has been made millions of times, in all proportions and quantities, for painting of fhips, and the outfide of wooden houfes, and fometimes intentionally, fometimes accidentally, left covered or open, a longer or a fhorter time, fhould be capable of kindling of itself. It is highly probable, that, even on this occafion, it was entirely owing to the attention of the emprefs that it was made an object of inquiry, or even that it was at all obferved.

Before I finish this paper, I will juft mention a felf-accenfion, ret noticed till of late, and that by Mr. Hagemann, an apothecary, at Bre men. He prepared a boiled oil of hyoscyamus, or henbane, in the ufual way, with common oil. The humidity of the herb was nearly evaporated, when he was called away by other affairs, and was obliged to leave the oil on the fire. The evaporation of the humidity was hereby carried fo far, that the herb could eafily be rubbed to powder. The oil had loft its green colour, and had become brownish. In this ftate it was laid on the ftraining cloth, and placed in the garden, behind the houfe, in the open air. 3